Until recently, it had been thought that the host range of Agrobacterium tumefaciens was limited only to dicotyledenous plants. This conclusion rested on the observation that when monocotyledonous plants were infected with this bacterium there was apparently no oncogenic response. It has now been demonstrated that the degree of cell proliferation among monocots in response to infection is quite.broad and host specific. Support is requested to determine the molecular basis for the wide range of oncogenic response when T-DNA transforms susceptible monocots. Specifically, answers to the following questions are sought using Southern and Northern analyses, (i) Is the T-DNA present in these cell lines as an independent episome or does it become covalently linked to a member of the host genomic complement? (ii) If the T-DNA is chromosome linked, how many copies are inserted per genomic comPlement? (iii) If the T-DNA sequences are present in transformed monocot cells, are tms and tmr transcribed, yielding mRNA populations similar to those isolated from dicot tumors? (iv) In those species such as Zea, which yield no proliferative response, or Narcissus. from which is elicited a minimal one, are the entire onc sequences still present in the transforming T-DNA?